This invention relates to fluorescent optical fibers and more particularly to the diagnosis of the nature or condition of an excitation beam and/or the environment of the optical fiber by an analysis of the emitted fluorescence from the fiber.
In recent years, optical fibers have been developed with doped cores that will fluoresce at a relatively long wavelength when the core is pumped by light of a shorter wavelength. For example, an optical fiber has been developed by York Ventures of Special Optical Products Ltd., Hampshire, England, having a core of germano-silicate (GeO.sub.2 -SiO.sub.2) glass doped with neodymium ions (Nd.sup.3+) which will fluoresce in a broad band from 850 to 985 nanometers with a peak at 950 nanometers in the near-infrared when pumped by light of 510 and/or 585 nanometers. Such fibers have been used for fiber lasers, fiber amplifiers, temperature sensors and for wavelength filtering.
Also, for example, a fiber has been developed by Bicron Corporation, Newbury, Ohio, wherein a plastic scintillating fiber with a polystyrene doped core will fluoresce in the ultraviolet region when the core is excited by charged particles or neutrons. The ultraviolet light is then converted into visible light by fluorescent dye present within the fiber. Such fibers have been commonly used in particle physics experiments.
Other diagnostic uses of fluorescent fibers have been in the detection of color changes in the fluorescent materials in the presence of chemicals.
The present invention relates to new uses of fluorescent optical fibers to diagnose the condition of the excitation and/or environment of a fluorescent fiber by an evaluation of the fluorescence emitted from an end of the fiber.
SUMMARY OF THE INVENTION
It is the principal object of the invention to provide a method for evaluating the excitation or environment of an excited fluorescent fiber by an evaluation of the fluorescence in the fiber.
Additional objects, advantages and novel features will be set forth in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of instrumentalities and combinations pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the present invention as described and broadly claimed herein, a diagnostic method is provided using a fluorescing optical fiber having a doped core that will fluoresce at one wavelength when pumped by light of another wavelength, wherein the core is pumped with light to cause fluorescence in the core, wherein the fluorescence emitted from an end of the fiber is detected, and wherein the degree of intensity of the detected fluorescence is monitored.
A further aspect of the invention is that when the excitation light is from a copper-vapor laser, an 15 optical fiber with a neodymium-doped core is used for fluorescence at around 950 nanometers in response to absorption of green and yellow light from the copper-vapor laser at 510 and 578 nanometers.